In order to estimate uncertainty based on QC and validation dasta the method has to be in routine use for some time, preferable more than 6 months. Preliminary uncertainty can be taken from the standard method or from PT reports. In some standard method is presented in appendix results from precision studies according to ISO 5725. Here you can find s(R), the reproducibility and this can, if we assume that the method bias is under control, be set equal to the combined standard uncertainty u(c). The preliminary expanded uncertainty, U, can the be calculated: